Enzymes are being increasingly used in industrial applications and processes. Proteolytic enzymes are valuable ingredients in many reactions required in food processing (e.g., clarification of juices, beer, wine, etc.; tenderization of meats: preparation of hydrolyzed protein materials for food application; preparation of specialized hydrolyzed proteins for special dietary requirements). In addition, proteases are used in detergents which represent a major market. Furthermore, specific proteases may have advantages in facilitating the isolation of high value products produced using modern biotechnology.
It is estimated that enzyme sales for food applications should surpass 0.3 billion dollars in 1986. The market for proteolytic enzymes in detergents is very large and the market in the area of biomedical and biochemical applications is very significant.
However, the application of enzymatic catalysis to fine organic synthesis, medicine, and the food industry is often hindered because many enzymes, when subjected to temperatures higher than those found in their natural environment, become unstable and rapidly inactivate or denature. Hence, the art of enzyme stabilization toward heat denaturation has become the subject of intense interest in recent years. Modification of the heat stability of certain proteins, as in enhancing the thermal stability of some enzymes used in food and beverage manufacture or as in-place-cleaning (IPC) agents for processing equipment, requires an understanding of the relationship between a protein's structure and its inherent thermal stability.
A major obstacle limiting more widespread use of enzymes is their high cost. Reduction in cost may be achieved by more efficient production using biotechnology and by enhancing the stability of enzymes. In this regard, thermostability is a highly desirable trait in enzymes for the food biomedical, and detergent industry. Thermostability connotes the retention of enzyme activity upon exposure to temperatures above 60.degree. C. for prolonged periods.
Thermostability is desirable because the efficiency of enzymes is markedly improved at higher temperatures. Thus, less enzyme is required in particular applications. Also, holding times for specific processes can be shortened thereby minimizing undesirable chemical reactions. This is particularly valuable in food processing where nutrients may be lost during processing at high temperatures. In addition, conducting thermal processes at higher temperatures minimizes microbial contamination. This is particularly important for food safety and for preparation of special hydrolyzed products for therapeutic diets.
In addition to thermal stability, broad substrate specificity and pH tolerance, particularly tolerance to alkaline pH values, are very desirable traits for many food processing applications but more importantly, for enzymes to be used in the detergent industry. For use in detergents, it is desirable to have a thermostable alkaline tolerant broad specificity type of protease which makes it compatible with the alkaline detergents and the temperature of warm washing water.